thanks for the answers.. i dont look for the easiest way .. should be a bit more work.. but nothing like switching electronic (because of money) and swift to one-engine or other engine mountings..

i bought this boat, because they said this has a controller for 50A .. so i think thats enough..

but one question:
the stock eninges run at 7,2V each or 14,4V ? i cant test it at the moment.. i thought about 7,2V for each in row.. so it goes to 14,4v together.. is it right??